Starting and operating circuit for hot cathode gaseous discharge lamps



Nov. 2, 1943. WA. WARREN STARTING AND OPERATING CIRCUIT FOR HOT CATHQDE GASEOUS DISCHARGE LAMPS Filed Oct. 30, 1940 H i TTORNEY' MMA Patented Nov. 2, 1943 I a arms s'raa'rmc ornnarnvo. cmcorr non or ca'rnonn GASEOUS mscnaacs William 1;. Warren, Hurley, N. Y. Application October 30, 1940, Serial No. 363,422 Claims. (01.176-124) .The invention relates to anvimproved starting and operating circuit for hot cathode gaseous discharge lamps, in which it is necessaryv or desirable to preheat the cathodes to start the arc current, or discharge throughthe lamp, and in which it is necessary toregulate or control this current after the [arc ordischarge current has been started. 1

series capacitors and one shunt inductance. It

' shows a diflerent method of coupling the filament heating circuits into the constant current circuits. Figs. 4 and 5 are similar drawings showing I bridge circuits each having two inductances vMost lamps of this character have what is known as negative voltage resistancecharacteracross the terminals of the lamp to maintain a large current, than it-does to maintain a small current; Some device or switch has to be used to preheat the cathodes, and this is then operated 'to apply voltage to the lamp to start the arc.

The present invention overcomes these objections and provides a. quick means of starting these lamps. These lamps are inoperative on 'a' .constant voltage source, unless some seriesimpedance or other method of controlling the cur-f rent is used. The process of starting and oper-- ating is accomplished. by coupling a hot cathode discharge lamp into a substantially constant current circuit. The invention consists in the means for the control of current througha'discharge tube havingv two heatedelectrodes that alternately actas cathodes, by connecting same into a circuit which converts a constant potential.

source into a constant current in such a way by conductive or inductive coupling,- the cathodes I or filaments are heated quickly by the inrush of" isticathat is, it takes a lower voltage impressed current, inherent in these constant current circuits when the. output terminals are open-circuited that is before the arc discharge'is started, and at the same time impressing ahigh voltage between these two electrodes orcathodes to start the flow ofv the normal arc current. By. the nature of these circuits as sconas the output circuit is established,'that-is as soon as'the arc current through the lamp starts, vthe inrush of current is reduced and the vcltage'applied to heat the filaments caused by greatly reduced. 1 The principle of the invention having been set the initial rush is also forth, the following embodimentsthereoi' are 'described and shown to enable a man art to reprcducethe same.

In the accompanying drawing: v .Figs. 1 and 2 are diagrammatic drawings of'T circuits having series inductances and a shunt g capacitor... They each show" a diflere'nt' method of-coupling ,the filament heating circults lnto""" 1 some part of the constant current circuit; v

- Fig. 3 is-a similar drawing of a-Tcircuit with skilled in the and two-capacitors. These twodrawings show ,two methods difl'ering slightlyof coupling the filament heating circuits into the constant current circuit. In both of these circuits the iii-*- ductances ,L1 and L: are shown as separate units: but it is usuallyv desirable to wind both coils on one iron core, insulated from each other but connected in such a way that the mutual inductance between the two. coils adds to the self-inductance.

Fig. 6 shows another form of the bridge circuit similar. toFlg. 5 but having two. additional inductances In and Lt connected as shown. These two inductances may be .wound one. common iron core but not on the same core as L; and In. These small inductances prevent the circulating of any harmonic or otherv high frequency currents that may be generated by the lamp from flowing back to the supply line through condensers C1 and Ca.

. Similar characters 01' reference indicate simithe various views, where lar parts throughout appropriate.---

I Referring w ng. 1, the 1- circuit with series inductances'Li and In represent inductances of appropriate value'to give the desired cur'rent through the lamp D when an alternating current voltage of given value and frequency is impressed across the input terminals. At the center of the drawing C is a capacitor of appropriate value. L1 and Lainductances are coils wound on iron cores with an air gap inthe magnetic circuit. Coils A and B are wound onthe same iron core as L1, but are electrically insulated from L1. The

terminals of A and B are connected respectively" to the upper and lower electrodes. or cathodes of the lamp, D, which is a .hot cathode discharge.

lamp, F is a fuse or other current interrupting device- The method of operation is as follows:

In starting, alternating current voltage is applied to terminals. -A s L1 and .C are designed to be in resonance at the frequency of the alternating' current used, a large current will flow from one line terminal through' inductance L1. and capacitor C. as they are designed to be in iresonance, (that is the reactive impedance of L1 is equal 'to and.-o f..opp0site signfto the capacitive? impedanceoiTC). I: This currentis" only: limited b the resistance losses in L1 andlosse's-in g aii also by magnetic saturation in. iron used in core ofLi and can be given any desired value by the design of L1. This large current produces large voltage across L1 and C but of nearly opposite phase relation.

induces voltages in each of coils A and B which are applied to upper and lower cathodes of lamp D. Coils A and B are so designed that these voltages are of proper value to quickly heat the filaments to the desired temperature for starting of the lamp. At the same time'the coils A and B supply heating current to the cathodes, a large voltage occurs across capacitor C. This high voltage in connection with the heated filaments starts the arc or discharge through lamp D. As soon as this discharge current has reached the value for which the circuit is designed the currents through L1and C are greatly reduced aixd the voltage across them is reduced proportionately. Also the voltage across coils A and Bzis reduced, thus reducing the heating our- 1 rent through the cathodes of lamp D.

In is another inductance similar to L1, in series sary to start the lamp but would open the supply line in case this current was sustained for a length of time that would overheat or endanger the circuit, which would be the case if lamp D failed or was removed from the circuit.

Fig. 2 shows another method of coupling filament heating currents to 'a T circuit. This circuit has a three winding transformer E; one winding in series with capacitor 0, one winding connected across upper filament of lamp D and the other winding across lower filament of lamp D. The large current through capacitor C in starting, and through the primary of E causes currents to fiow through the two cathodes of lamp D at the same time that high voltage is impressed between the two cathodes. After are or discharge current through lamp D is established, current through C, and primary of E, and consequently through secondaries of E and filaments, is reduced. F is a fuse or circuit breaking device as described for other circuits. Fig. 3 shows a T circuit using two capacitors C1 and C: and one inductance L1. The operation is similar to that described in connection with Figs. 1 and 2.

In starting the high current through capac- V itor C1 and inductance L1, causes voltages to be generated in coils A and -B which are inductively coupled to L1, which voltages cause currents to circulate in the two electrodes of lamp D to which they are respectively connected.

Fig. 4 shows a bridge circuit using two inductances. L1 and In and two capacitors C1 and C2 connected as shown. The lamp cathodes are connected one in each side of the circuit. One

between-L1 and C2, the other between C1 and In. Upon applying line voltage to terminals at left a large current will flow through L1 lamp filament at left, (to heat this filament) and C2 back to line. The same occurs through right side of circuit heating said filament of lamp. L1 and C2, also C1 and In, are in resonance. The

The large current through L1 creates a large magnetic flux. in core of L1 which voltage across L1 and C1 will be of nearly opposite phase so that a large voltage will be impressed across the two opposite filaments of the lamp, thus starting the arc discharge through the lamp, and as soon as this current is established the current through the filaments is greatly reduced. F is a fuse or other current limiting device in the supply line to protect circuit in case of failure of lamp to start. In this particular circuit no excess voltage or current can occur if the lamp is removed from circuit as the circuit will be opened at two opposite corners.

This particular circuit is suitable only for lamps where filament heating current is of proper value, the same as circulating current in bridge arms when this produces the proper voltage to start the lamp.

Inductances L1 and L2 may be wound on the same iron core and so connected as to be mutually additive in inductance. v

Fig. 5 shows a modification of Fig. 4. This is the same as Fig. 4 except that inductances L1 and L2 are each tapped at the filament end so as to supply proper voltages across filaments where the simpler circuit of Fig. 4 does not furnish the proper heating current to these filaments. F is a fuse,'as before described.

Fig. 6 is still another modification of Figs. 4 and 5. The modification consists in inserting in series with capacitor C1 a self inductance L: and in series with capacitor C: a self inductance L4. These two'inductances Ia and L4 may'be wound on a common core. The advantage of this arrangement over the two previously described is that C1 and C: can be made of smaller capacity and operated at higher voltage than in the other circuits. In and L1 also tend to prevent circulation of the harmonic and higher frequencies from line through C1, the lamp O2 and back to other side of line. Additional coils Li and L4 as shown in Fig. 6 may be used in the circuit of Fig. 4 where the circulating current is of proper value for heating filaments. These coils as above prevent circulation of undesired higher frequency currents. L1 and In can be wound on one core, which is desirable for saving of material.

Also in Fig. 6, L: and L4 can be wound on the same core, but not on same core with L1 and In. In the circuits previously described, it is pos-' sible to substantially vary the power factor of alternating current supplied to the device and also the phase angle of the current through the lamp in respect to the supply voltage by changing the constants of the circuit (values of in- I ductance of the coils and/or values of capacitors) without materially impairing other desirable features of the circuit.

I have shown various embodiments, but various changes can be made therein without departing from the principle of the invention.

What I claim is:

1. An electric circuit adapted to supply startass including inductive reactances of values such that the voltages at opposite ends of the lamp are in substantially opposite phase, whereby a starting voltagewili be impressed across the lamp which is higher than the operating voltage.

2. In combination, a T circuit comprising series inductive reactances and at least one capacitative reactance, one of said inductive reactances being the primary of an induction coil which is provided with two secondary coils, said reactances being connected to asource of alternating current and having such values as to produce a condition of resonance in said' 'serles circuit, a second circuit comprising a series reactance and a hot cathode discharge lamp, having electrically heated filaments supplied with a heating current by the secondary coils of said transformer, said second circuit being connect-" ed in shunt across one of the reactances of said first circuit, whereby the starting voltage and filament heating current initially supplied to said lamp are substantially higher than the operating values.

3. An electric circuit adapted to supply starting and operating voltages to hot cathode dishaving four bridge arms with a source of alternating current connected across two opposite conjugate points oi the bridge and a hot cathode discharge lamp connected across the other two conjugate points, one pair of opposed bridge arms comprising inductive reactancesand the other pair comprising inductive a-eactances. in

series with condensative reactances or valuessuchithat the voltages at opposite ends of thelamp are in substantially opposite phase, where'- by a starting voltage will be impressed across the lamp which is higher than the operating -voltage.\

4. The electric circuit of claim 3 wherein the filaments 01' said discharge lamp are connected in the bridge network in series between the bridge arms at said other two coniugate points. 5. The electric circuitof claim 3 wherein the filaments of -said. discharge lamp are connected'in shunt across portions of said inductive re, actance in said bridge network in such manner that they are heated by the resultinginduced currents.

wnmma. WAR-arm.

charge lamps which comprises a bridge network 

